Jobs didn't have to start up Next for us to have iOS devices now. Surely there were a lot more UNIX derivatives than what they did at Next. If none of this happened, Microsoft wouldn't be the tech giant they became in the 90's, that would be Apple because Mac OS would be the Windows of the world then. So basically everything would have been different, and an Apple not struggling to stay afloat might have innovated a lot more a lot earlier than what we got in our timeline.
Things would be a lot different, that's for sure. First though, you have to wonder why Apple ended up struggling for survival back in the day. Was it because MS steamrolled them over, or because they didn't offer the market much of a compelling choice in comparison, despite being the "first" GUI OS manufacturer. It's really a mix of both. MS played dirty, but Apple practically gave them the entire market to do with as they pleased by not doing much of anything at all to combat them.
Now if Apple had exclusive rights to the GUI back then, you can just look at history and see that things would've likely been considerably worse. Even when they had every reason in the word to innovate during those post-Jobs years, they didn't. If they had exclusive control of the market, it probably would've ended up more staid and blase than what we had with MS during the late '90's, early '00's...and there would be no room for the market to grow for 30 years. Not while they held exclusive rights to all the patents involving the GUI.
One thing that the history of technology should teach you in general is that big companies don't innovate unless they absolutely have to. Look at AT&T. They invented voice telecommunication. Yet while they held their decades long monopoly, barely any advances were made in that field. It wasn't until the government busted them up in the early 80's that things started moving, and we started seeing real innovations in the field again.
...and now everything is reconsolidating here in the US, and we're all getting shafted on prices.
What makes you think Apple would've been any different had they almost complete control of the GUI PC market?